Semiconductor devices including field effect transistors and methods of forming the same

ABSTRACT

A semiconductor device includes an active pattern provided on a substrate and a gate electrode crossing over the active pattern. The active pattern includes a first buffer pattern on the substrate, a channel pattern on the first buffer pattern, a doped pattern between the first buffer pattern and the channel pattern, and a second buffer pattern between the doped pattern and the channel pattern. The doped pattern includes graphene injected with an impurity.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/591,405, filed on May 10, 2017, which is a divisionalapplication of U.S. patent application Ser. No. 14/823,229, filed onAug. 11, 2015, now U.S. Pat. No. 9,679,975, issued on Jun. 13, 2017,which claims the benefit of Korean patent application number10-2014-0159871, filed on Nov. 17, 2014, in the Korean IntellectualProperty Office, the contents of which applications are incorporatedherein in their entirety by reference.

BACKGROUND

The inventive concepts relate to semiconductor devices and methods offorming the same. More particularly, the inventive concepts relate tosemiconductor devices including field effect transistors and methods offorming the same.

Semiconductor devices are widely used in the electronic industry becauseof their small sizes, multi-functional characteristics, and/or lowmanufacture costs. Semiconductor devices may be categorized as any oneof semiconductor memory devices storing data, semiconductor logicdevices processing operations of logical data, and hybrid semiconductordevice having both the function of the semiconductor memory devices andthe function of the semiconductor logic devices. High-reliable,high-speed, and/or multi-functional semiconductor devices have beenincreasingly demanded. To satisfy these demands, structures ofsemiconductor devices have been complicated and semiconductor deviceshave been highly integrated.

SUMMARY

Exemplary embodiments in accordance with principles of inventiveconcepts may provide semiconductor devices capable of improvingoperating characteristics and reliability and methods of forming thesame.

Exemplary embodiments in accordance with principles of inventiveconcepts may also provide semiconductor devices capable of easilyproviding semiconductor components that are formed of the same channelmaterial and have conductivity types different from each other andmethods of forming the same.

Exemplary embodiments in accordance with principles of inventiveconcepts may also provide semiconductor devices capable of easilyproviding semiconductor components that are formed of the same channelmaterial and have threshold voltages different from each other andmethods of forming the same.

In exemplary embodiments in accordance with principles of inventiveconcepts, a semiconductor device may include: an active pattern providedon a substrate; and a gate electrode provided on the active pattern andintersecting the active pattern. The active pattern may include: a firstbuffer pattern on the substrate; a channel pattern on the first bufferpattern; a doped pattern between the first buffer pattern and thechannel pattern; and a second buffer pattern between the doped patternand the channel pattern. The doped pattern may include graphene injectedwith an impurity.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern may have a conductivity type of a P-type oran N-type.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern may provide extra carriers to the channelpattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, an impurity concentration of the doped pattern may be higherthan 1×10⁶/cm² and equal to or lower than 1×10¹²/cm².

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern may have a crystal structure formed bysubstituting the impurity for some of carbon atoms of the graphene.

In exemplary embodiments in accordance with principles of inventiveconcepts, the first buffer pattern and the second buffer pattern mayinclude the same material.

In exemplary embodiments in accordance with principles of inventiveconcepts, the active pattern may further include: a barrier pattern onthe channel pattern. The channel pattern may be disposed between thesecond buffer pattern and the barrier pattern. The channel pattern mayinclude a material of which an energy band gap is smaller than those ofthe second buffer pattern and the barrier pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the channel pattern may include a group compound.

In exemplary embodiments in accordance with principles of inventiveconcepts, the semiconductor device may further include: a deviceisolation layer provided on the substrate to define the active pattern.The active pattern may include an upper portion exposed by the deviceisolation layer, and a height of a top surface of the device isolationlayer may be lower than a height of a bottom surface of the dopedpattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the upper portion of the active pattern may be defined as anactive fin. The gate electrode may cover a top surface and bothsidewalls of the active fin and may extend onto the top surface of thedevice isolation layer.

In exemplary embodiments in accordance with principles of inventiveconcepts, the active pattern may include a plurality of active patterns.The gate electrode may intersect the plurality of active patterns, andthe doped patterns of the plurality of the active patterns may have thesame conductivity type.

In exemplary embodiments in accordance with principles of inventiveconcepts, a semiconductor device may include: a first active pattern anda second active pattern spaced apart from each other on a substrate; anda first transistor and a second transistor comprising the first activepattern and the second active pattern, respectively. Each of the firstand second active patterns may include: a first buffer pattern on thesubstrate; a channel pattern on the first buffer pattern; a dopedpattern between the first buffer pattern and the channel pattern; and asecond buffer pattern between the doped pattern and the channel pattern.The doped pattern may include graphene injected with an impurity.

In exemplary embodiments in accordance with principles of inventiveconcepts, a conductivity type of the doped pattern of the first activepattern may be different from that of the doped pattern of the secondactive pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the channel pattern of the first active pattern may includethe same material as the channel pattern of the second active pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the channel patterns of the first and second active patternsmay include a III-V group compound.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern of the first active pattern may have aP-type when the first transistor is a PMOS field effect transistor. Thedoped pattern of the second active pattern may have an N-type when thesecond transistor is an NMOS field effect transistor.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern of the first active pattern may have thesame conductivity type as the doped pattern of the second activepattern, and an impurity concentration of the doped pattern of the firstactive pattern may be different from an impurity concentration of thedoped pattern of the second active pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the channel pattern of the first active pattern may includethe same material as the channel pattern of the second active pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the channel patterns of the first and second active patternsmay include a III-V group compound.

In exemplary embodiments in accordance with principles of inventiveconcepts, the first transistor may have the same conductivity type asthe second transistor, and a threshold voltage of the first transistormay be different from a threshold voltage of the second transistor.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped pattern may provide extra carriers to the channelpattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, the first transistor and the second transistor may share onegate electrode. The one gate electrode may be provided on the substrateto intersect the first active pattern and the second active pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts, a method of forming a semiconductor device may include:forming a first buffer layer on a substrate; providing a graphene layeronto the first buffer layer; injecting the graphene layer with animpurity; forming a second buffer layer on the graphene layer injectedwith the impurity; forming a channel layer on the second buffer layer;sequentially patterning the channel layer, the second buffer layer, thegraphene layer injected with the impurity, and the first buffer layer toform an active pattern protruding in a direction perpendicular to a topsurface of the substrate; and forming a gate electrode intersecting theactive pattern. The graphene layer injected with the impurity mayprovide extra carriers to the channel layer.

In exemplary embodiments in accordance with principles of inventiveconcepts, injecting the graphene layer with the impurity may include:injecting a portion of the graphene layer with a first impurity to forma first doped region having a first conductivity type; and injectinganother portion of the graphene layer with a second impurity to form asecond doped region having a second conductivity type different from thefirst conductivity type. The active pattern may include a first activepattern including the first doped region and a second active patternincluding the second doped region.

In exemplary embodiments in accordance with principles of inventiveconcepts, injecting the graphene layer with the impurity may include:injecting a portion of the graphene layer with a first impurity to forma first doped region; and injecting another portion of the graphenelayer with a second impurity to form a second doped region. The firstdoped region may have the same conductivity type as the second dopedregion, and a concentration of the first impurity in the first dopedregion may be different from a concentration of the second impurity inthe second doped region. The active pattern may include a first activepattern including the first doped region and a second active patternincluding the second doped region.

In exemplary embodiments in accordance with principles of inventiveconcepts, providing the graphene layer onto the first buffer layer mayinclude: forming the graphene layer on a support substrate; andtransferring the graphene layer from the support substrate onto thefirst buffer layer.

In exemplary embodiments in accordance with principles of inventiveconcepts, forming the second buffer layer may include: forming thesecond buffer layer on a support substrate, the second buffer layerhaving a first surface being in contact with the support substrate and asecond surface opposite to the first surface; providing the secondbuffer layer and the support substrate onto the graphene layer injectedwith the impurity such that the second surface of the second bufferlayer is in contact with the graphene layer injected with the impurity;injecting hydrogen ions into the second buffer layer to form aninterface; and physically removing the support substrate and a portionof the second buffer layer by using the interface. The second bufferlayer may be divided into an upper portion adjacent to the supportsubstrate and a lower portion adjacent to the graphene layer injectedwith the impurity by the interface. The upper portion of the secondbuffer layer may be physically separated and removed from the lowerportion of the second buffer layer.

In exemplary embodiments in accordance with principles of inventiveconcepts, a method of forming a semiconductor device may include:forming a first buffer layer on a substrate; forming a graphene layerdoped with an impurity on the first buffer layer; patterning the dopedgraphene layer to form doped patterns; and forming a second buffer layerby performing a selective epitaxial growth (SEG) process using a topsurface of the first buffer layer exposed by the doped patterns as aseed. The second buffer layer may fill a space between the dopedpatterns and may extend onto top surfaces of the doped patterns.

In exemplary embodiments in accordance with principles of inventiveconcepts, the doped patterns may be buried under the second bufferlayer.

In exemplary embodiments in accordance with principles of inventiveconcepts, the method may further include: forming a channel layer on thesecond buffer layer; sequentially patterning the channel layer, thesecond buffer layer, and the first buffer layer to form active patternsprotruding in a direction perpendicular to a top surface of thesubstrate; and forming a gate electrode intersecting the activepatterns. The second buffer layer disposed between the doped patternsmay be etched during the patterning process. The active patterns mayinclude the doped patterns, respectively.

In exemplary embodiments in accordance with principles of inventiveconcepts, a semiconductor device may include: a device isolation layerprovided on a substrate to define an active pattern; and a gateelectrode provided on the active pattern and intersecting the activepattern. The active pattern may include: a first buffer pattern on thesubstrate; a channel pattern on the first buffer pattern; a dopedpattern between the first buffer pattern and the channel pattern; and asecond buffer pattern between the doped pattern and the channel pattern.The doped pattern may provide extra carriers to the channel pattern, anda height of a bottom surface of the device isolation layer may be lowerthan a height of a bottom surface of the first buffer pattern.

In exemplary embodiments in accordance with principles of inventiveconcepts a semiconductor device includes a first combination of firstand second field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel formed thereover; and asecond combination of first and second field effect transistors (FETs)of different conductivity, wherein each FET includes a doped graphenelayer between first and second buffer layers and a gate and channel.

In exemplary embodiments in accordance with principles of inventiveconcepts a semiconductor device includes a combination of first andsecond field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel formed thereover that formsa logic circuit.

In exemplary embodiments in accordance with principles of inventiveconcepts a semiconductor device includes a combination of first andsecond field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel formed thereover that formsa memory circuit.

In exemplary embodiments in accordance with principles of inventiveconcepts an electronic system includes a semiconductor device thatincludes a first combination of first and second field effecttransistors (FETs) of different conductivity, wherein each FET includesa doped graphene layer between first and second buffer layers and a gateand channel formed thereover; and a second combination of first andsecond field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel.

In exemplary embodiments in accordance with principles of inventiveconcepts a mobile electronic device includes a semiconductor device thatincludes a first combination of first and second field effecttransistors (FETs) of different conductivity, wherein each FET includesa doped graphene layer between first and second buffer layers and a gateand channel formed thereover; and a second combination of first andsecond field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel.

In exemplary embodiments in accordance with principles of inventiveconcepts a mobile telephone includes a semiconductor device thatincludes a first combination of first and second field effecttransistors (FETs) of different conductivity, wherein each FET includesa doped graphene layer between first and second buffer layers and a gateand channel formed thereover; and a second combination of first andsecond field effect transistors (FETs) of different conductivity,wherein each FET includes a doped graphene layer between first andsecond buffer layers and a gate and channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concepts will become more apparent in view of the attacheddrawings and accompanying detailed description.

FIG. 1A is a plan view illustrating a semiconductor device according toa first embodiment of the inventive concepts;

FIGS. 1B and 1C are cross-sectional views taken along lines I-I′ andII-II′ of FIG. 1A, respectively;

FIG. 1D is a cross-sectional view corresponding to the line II-II′ ofFIG. 1A to illustrate a semiconductor device according to a modifiedembodiment of a first embodiment of the inventive concepts;

FIGS. 2 to 5 are cross-sectional views corresponding to the lines I-I′and II-II′ of FIG. 1A to illustrate a method of forming a semiconductordevice according to a first embodiment of the inventive concepts;

FIG. 6 is a cross-sectional view corresponding to the line II-II′ ofFIG. 1A to illustrate a method of forming a semiconductor deviceaccording to a modified embodiment of a first embodiment of theinventive concepts;

FIGS. 7A, 7B, and 7C are conceptual diagrams illustrating a method offorming a graphene layer on a first buffer layer;

FIGS. 8A, 8B, and 8C are conceptual diagrams illustrating a method offorming a second buffer layer on a doped graphene layer;

FIG. 9A is a plan view illustrating a semiconductor device according toa second embodiment of the inventive concepts;

FIGS. 9B, 9C, and 9D are cross-sectional views taken along lines I-I′,II-II′, and III-III′ of FIG. 9A, respectively;

FIG. 9E is a cross-sectional view corresponding to the line III-III′ ofFIG. 9A to illustrate a semiconductor device according to a modifiedembodiment of a second embodiment of the inventive concepts;

FIGS. 10A to 13A are plan views illustrating a method of forming asemiconductor device according to a second embodiment of the inventiveconcepts;

FIGS. 10B to 13B are cross-sectional views taken along lines I-I′,II-II′, and III-III′ of FIGS. 10A to 13A, respectively;

FIG. 14 is a cross-sectional view corresponding to the line III-III′ ofFIG. 13A to illustrate a method of forming a semiconductor deviceaccording to a modified embodiment of a second embodiment of theinventive concepts;

FIG. 15A is a plan view illustrating a semiconductor device according toa third embodiment of the inventive concepts;

FIGS. 15B, 15C, 15D, and 15E are cross-sectional views taken along linesI-I′, II-II′, III-III′, and IV-IV′ of FIG. 15A, respectively;

FIG. 15F is a cross-sectional view corresponding to the line IV-IV′ ofFIG. 15A to illustrate a semiconductor device according to a modifiedembodiment of a third embodiment of the inventive concepts;

FIGS. 16A to 20A are plan views illustrating a method of forming asemiconductor device according to a third embodiment of the inventiveconcepts;

FIGS. 16B to 20B are cross-sectional views taken along lines I-I′ andII-II′ of FIGS. 16A to 20A, respectively;

FIGS. 16C to 20C are cross-sectional views taken along lines III-III′and IV-IV′ of FIGS. 16A to 20A, respectively;

FIG. 21 is a cross-sectional view corresponding to the line IV-IV′ ofFIG. 20A to illustrate a method of forming a semiconductor deviceaccording to a modified embodiment of a third embodiment of theinventive concepts;

FIGS. 22A to 26A are plan views illustrating a method of forming asemiconductor device according to a fourth embodiment of the inventiveconcepts;

FIGS. 22B to 26B are cross-sectional views taken along lines I-I′ ofFIGS. 22A to 26A, respectively; and

FIG. 27 is a schematic block diagram illustrating an electronic systemincluding a semiconductor device according to exemplary embodiments inaccordance with principles of inventive concepts.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The inventive concepts will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the inventive concepts are shown. The advantages and features of theinventive concepts and methods of achieving them will be apparent fromthe following exemplary embodiments that will be described in moredetail with reference to the accompanying drawings. It should be noted,however, that the inventive concepts are not limited to the followingexemplary embodiments, and may be implemented in various forms.Accordingly, the exemplary embodiments are provided only to disclose theinventive concepts and let those skilled in the art know the category ofthe inventive concepts. In the drawings, embodiments of the inventiveconcepts are not limited to the specific examples provided herein,features of which may be exaggerated for clarity.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit the invention. As usedherein, the singular terms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. It will beunderstood that when an element is referred to as being “connected” or“coupled” to another element, it may be directly connected or coupled tothe other element or intervening elements may be present.

Similarly, it will be understood that when an element such as a layer,region or substrate is referred to as being “on” another element, it canbe directly on the other element or intervening elements may be present.In contrast, the term “directly on” means that there are no interveningelements. It will be further understood that the terms “comprises”,“comprising,”, “includes” and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Additionally, an embodiment in the detailed description will bedescribed with sectional views as ideal exemplary views of the inventiveconcepts. Accordingly, shapes of the exemplary views may be modifiedaccording to manufacturing techniques and/or allowable errors.Therefore, the embodiments of the inventive concepts are not limited tothe specific shape illustrated in the exemplary views, but may includeother shapes that may be created according to manufacturing processes.Areas exemplified in the drawings have general properties, and are usedto illustrate specific shapes of elements. Thus, this should not beconstrued as limiting to the scope of the inventive concepts.

It will also be understood that although the terms first, second, thirdetc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another element. Thus, a first element insome embodiments could be termed a second element in other embodimentswithout departing from the teachings of the present invention. Exemplaryembodiments of aspects of the present inventive concepts explained andillustrated herein include their complementary counterparts. The samereference numerals or the same reference designators denote the sameelements throughout the specification.

Moreover, exemplary embodiments are described herein with reference tocross-sectional illustrations and/or plane illustrations that areidealized exemplary illustrations. Accordingly, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, exemplaryembodiments should not be construed as limited to the shapes of regionsillustrated herein but are to include deviations in shapes that result,for example, from manufacturing. For example, an etching regionillustrated as a rectangle will, typically, have rounded or curvedfeatures. Thus, the regions illustrated in the figures are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to limit the scope ofexample embodiments.

As appreciated by the present inventive entity, devices and methods offorming devices according to various embodiments described herein may beembodied in microelectronic devices such as integrated circuits, whereina plurality of devices according to various embodiments described hereinare integrated in the same microelectronic device. Accordingly, thecross-sectional view(s) illustrated herein may be replicated in twodifferent directions, which need not be orthogonal, in themicroelectronic device. Thus, a plan view of the microelectronic devicethat embodies devices according to various embodiments described hereinmay include a plurality of the devices in an array and/or in atwo-dimensional pattern that is based on the functionality of themicroelectronic device.

Devices according to various embodiments described herein may beinterspersed among other devices depending on the functionality of themicroelectronic device. Moreover, microelectronic devices according tovarious embodiments described herein may be replicated in a thirddirection that may be orthogonal to the two different directions, toprovide three-dimensional integrated circuits.

Accordingly, the cross-sectional view(s) illustrated herein providesupport for a plurality of devices according to various embodimentsdescribed herein that extend along two different directions in a planview and/or in three different directions in a perspective view. Forexample, when a single active region is illustrated in a cross-sectionalview of a device/structure, the device/structure may include a pluralityof active regions and transistor structures (or memory cell structures,gate structures, etc., as appropriate to the case) thereon, as would beillustrated by a plan view of the device/structure.

In accordance with principles of inventive concepts, a channel pattern,such as may be employed in a field effect transistor (FET) andelectronic devices that include FETs, may include a doped graphenelayer. The graphene layer may be a two-dimensional atomic scalehexagonal lattice in which one atom forms each vertex. One carbon atommay be two-dimensionally bonded to three carbon atoms to form ahoneycomb shape of graphene and the graphene may be injected or dopedwith an impurity to form a crystal structure with an impuritysubstituted for one or more of the carbon atoms of the graphene. Thedoped graphene may have a thickness of one atomic layer and extend in atwo-dimensional pattern, the extent of which is determined bypattern-processes. Devices may include complementary FETs, with devicesdoped to have different conductivity types (P- or N-type). Dopingconcentrations may differ between devices as well.

By employing doped graphene in accordance with principles of inventiveconcepts extra carriers may be available in a semiconductor device'schannel(s) and, as a result, the electrical conductivity in the channelmay be increased, thereby improving performance of the device and,because the doped graphene layer has a thickness of only one atom, thecharacteristic dispersion of an associated transistor may be enhanced.Additionally, the high thermal conductivity of the doped grapheneimproves heat dissipation of an associated device.

A device in accordance with principles of inventive concepts may includea gate formed over a channel which, in turn, is formed over first andsecond buffer layers sandwiching a doped graphene layer. With differentdoping, different devices may be P-type or N-type devices that may becombined to form an integrated device.

FIG. 1A is a plan view illustrating a semiconductor device according toa first exemplary embodiment of the inventive concepts. FIGS. 1B and 1Care cross-sectional views taken along lines I-I′ and II-II′ of FIG. 1A,respectively. FIG. 1D is a cross-sectional view corresponding to theline II-II′ of FIG. 1A to illustrate a semiconductor device according toa modified embodiment of a first exemplary embodiment of the inventiveconcepts.

Referring to FIGS. 1A, 1B, and 1C, a device isolation layer ST may beprovided on a substrate 100 to define an active pattern AP. The activepattern AP may have a bar, or elongated rectangular, shape extending ina first direction D1 when viewed from a plan view. Substrate 100 may bea semiconductor substrate formed of silicon, germanium, orsilicon-germanium or may be a silicon-on-insulator (SOI) substrate, forexample. The device isolation layer ST may include at least one of, forexample, an oxide layer, a nitride layer, or an oxynitride layer.

The active pattern AP may include a first buffer pattern 102 disposed onthe substrate 100, a channel pattern 108 disposed on the first bufferpattern 102, a doped pattern 104 disposed between the first bufferpattern 102 and the channel pattern 108, and a second buffer pattern 106disposed between the doped pattern 104 and the channel pattern 108.According to an exemplary embodiment, the active pattern AP may furtherinclude a barrier pattern 112 disposed on the channel pattern 108. Insuch exemplary embodiments, the channel pattern 108 may be disposedbetween the barrier pattern 112 and the second buffer pattern 106. Thedoped pattern 104 may be more adjacent to the channel pattern 108 thanto the substrate 100. That is, in such exemplary embodiments a distancebetween the doped pattern 104 and the channel pattern 108 may be smallerthan a distance between the doped pattern 104 and the substrate 100.

The first buffer pattern 102 may include silicon (Si), germanium (Ge),silicon-germanium (SiGe), or a III-V group compound. For example, theIII-V group compound may include aluminum phosphide (AlP), galliumphosphide (GaP), indium phosphide (InP), aluminum arsenide (AlAs),gallium arsenide (GaAs), indium arsenide (InAs), aluminum antimonide(AlSb), gallium antimonide (GaSb), or indium antimonide (InSb).

The doped pattern 104 may include graphene injected or doped with animpurity. In such exemplary embodiments, one carbon atom may betwo-dimensionally bonded to three carbon atoms to constitute a honeycombshape, and the graphene has a two-dimensional crystal structure havingthe honeycomb shape. The doped pattern 104 may have a crystal structureformed by substituting the impurity for one (or some) of the carbonatoms of the graphene. The doped pattern 104 may have a thickness t ofone atomic layer because of the two-dimensional crystal structure of thegraphene.

The doped pattern 104 may have a first conductivity type or a secondconductivity type different from the first conductivity type. Inexemplary embodiments, the first conductivity type may be a P-type, andthe second conductivity type may be an N-type. If the doped pattern 104has the first conductivity type, the impurity may include, for example,boron (B). Alternatively, if the doped pattern 104 has the secondconductivity type, the impurity may include halogen atoms (e.g.,nitrogen or fluorine). In some exemplary embodiments, a concentration ofthe impurity in the doped pattern 104 may be higher than 1×10⁶/cm² andequal to or lower than 1×10¹²/cm².

In a cross-sectional view, the doped pattern 104 may be more adjacent tothe channel pattern 108 than to the substrate 100. In such exemplaryembodiments, the doped pattern 104 may provide extra carriers to thechannel pattern 108. In the graphene, each carbon atom, and other carbonatoms adjacent thereto, may be bonded to each other to form three sigmabonds and one pi bond. One or some of the carbon atoms of the graphenemay be replaced with the impurity, so the extra carriers (e.g., holes orelectrons) may be generated and then transported to the channel pattern108 through the pi bond.

The second buffer pattern 106 may include the same material as the firstbuffer pattern 102. For example, the second buffer pattern 106 mayinclude silicon (Si), germanium (Ge), silicon-germanium (SiGe), or aIII-V group compound (e.g., aluminum phosphide (AlP), gallium phosphide(GaP), indium phosphide (InP), aluminum arsenide (AlAs), galliumarsenide (GaAs), indium arsenide (InAs), aluminum antimonide (AlSb),gallium antimonide (GaSb), or indium antimonide (InSb)). According toexemplary embodiments, the second buffer pattern 106 may include thesame material as the first buffer pattern 102 and may have the samecomposition ratio as the first buffer pattern 102. Alternatively, thesecond buffer pattern 106 may include the same material as the firstbuffer pattern 102, but the composition ratio of the second bufferpattern 106 may be different from that of the first buffer pattern 102.

The channel pattern 108 may include a material of which an energy bandgap is smaller than that of the second buffer pattern 106. In exemplaryembodiments, the channel pattern 108 may include a material of which anenergy band gap is smaller than those of the first and second bufferpatterns 102 and 106. For example, the channel pattern 108 may includesilicon (Si), germanium (Ge), silicon-germanium (SiGe), or a III-V groupcompound (e.g., aluminum phosphide (AlP), gallium phosphide (GaP),indium phosphide (InP), aluminum arsenide (AlAs), gallium arsenide(GaAs), indium arsenide (InAs), aluminum antimonide (AlSb), galliumantimonide (GaSb), or indium antimonide (InSb)). In exemplaryembodiments, the first buffer pattern 102, the second buffer pattern106, and the channel pattern 108 may be formed of the III-V groupcompounds. In such embodiments, the channel pattern 108 may be formed ofthe III-V group compound of which an energy band gap is smaller thanthose of the III-V group compounds of the first and second bufferpatterns 102 and 106.

The barrier pattern 112 may include a material of which an energy bandgap is greater than that of the channel pattern 108. That is, in suchembodiments the channel pattern 108 may include the material of whichthe energy band gap is smaller than those of the barrier pattern 112 andthe second buffer pattern 106, so the channel pattern 108 may have aquantum well structure. The barrier pattern 112 may include silicon(Si), germanium (Ge), silicon-germanium (SiGe), or a III-V groupcompound. In other exemplary embodiments, the barrier pattern 112 may beomitted.

According to exemplary embodiments, both sidewalls of the active patternAP may not be exposed by the device isolation layer ST, as illustratedin FIG. 1C. According to other exemplary embodiments, the active patternAP may include an upper portion (hereinafter, referred to as ‘an activefin AF’) exposed by the device isolation layer ST, as illustrated inFIG. 1D. That is, in such exemplary embodiments an upper portion of eachof the both sidewalls of the active pattern AP may be exposed by thedevice isolation layer ST. In such embodiments, a height of a topsurface STu of the device isolation layer ST may be lower than a heightof a bottom surface 104L of the doped pattern 104.

In some exemplary embodiments, a height of a bottom surface ST_L of thedevice isolation layer ST may be lower than a height of a bottom surface102L of the first buffer pattern 102, as illustrated in FIGS. 1C and 1D.

A gate electrode GE may be provided to intersect the active pattern AP.The gate electrode GE may be provided on the active pattern AP and mayextend in a second direction D2 intersecting the first direction D1. Inexemplary embodiments, the gate electrode GE may cover the top surfaceof the active pattern AP and the top surface of the device isolationlayer ST, as illustrated in FIG. 1C. In other exemplary embodiments, thegate electrode GE may cover the top surface and the exposed sidewalls ofthe active pattern AP and may extend onto the top surface of the deviceisolation layer ST, as illustrated in FIG. 1D.

In some exemplary embodiments, even though not shown in the drawings,the active pattern AP may be provided in plurality. In such embodiments,one gate electrode GE may intersect the plurality of active patterns AP.Each of the active patterns AP may include the first buffer pattern 102,the doped pattern 104, the second buffer pattern 106, and the channelpattern 108. Each of the active patterns AP may further include thebarrier pattern 112. The doped patterns 104 of the plurality of activepatterns AP may have the same conductivity type.

A gate insulating pattern GI may be provided between the gate electrodeGE and the active pattern AP. The gate insulating pattern GI may extendalong a bottom surface of the gate electrode GE in the second directionD2. According to exemplary embodiments, the gate insulating pattern GImay be in contact with the top surface of the active pattern AP and thetop surface of the device isolation layer ST, as illustrated in FIG. 1C.Alternatively, the gate insulating pattern GI may be in contact with thetop surface and the exposed sidewalls of the active pattern AP and mayextend onto the top surface of the device isolation layer ST so as to bein contact with the top surface of the device isolation layer ST, asillustrated in FIG. 1D.

A capping pattern CAP may be provided on a top surface of the gateelectrode GE, and gate spacers GS may be provided on both sidewalls ofthe gate electrode GE.

In exemplary embodiments, the gate insulating pattern GI may include atleast one of a high-k dielectric layer (e.g., a hafnium oxide layer, ahafnium silicate layer, a zirconium oxide layer, or a zirconium silicatelayer) or a silicon oxide layer, for example. The gate electrode GE mayinclude at least one of doped silicon, a metal, or a conductive metalnitride (e.g., titanium nitride (TiN) or tantalum nitride (TaN)). Thecapping pattern CAP and the gate spacers GS may include a nitride suchas silicon nitride.

Source/drain regions 110 may be provided in the active pattern AP atboth sides of the gate electrode GE. The source/drain regions 110 may belaterally spaced apart from each other with the channel pattern 108interposed therebetween. The channel pattern 108 may be locally disposedunder the gate electrode GE, and the source/drain regions 110 may beprovided at both sides of the gate electrode GE, respectively. Thesource/drain regions 110 and the channel pattern 108 may be provided onthe second buffer pattern 106. The source/drain regions 110 may includea conductive material. As illustrated in FIG. 1B, the source/drainregions 110 may be provided in the active pattern AP at both sides ofthe gate electrode GE. However, inventive concepts are not limitedthereto.

In exemplary embodiments in which a semiconductor component includingthe active pattern AP, the gate electrode GE and the source/drainregions 110 is an N-type metal-oxide-semiconductor (NMOS) field effecttransistor, the second buffer pattern 106 may provide a tensile strainto the channel pattern 108. In some exemplary embodiments, the secondbuffer pattern 106 may be formed of Si_(1-x)Ge_(x), and the channelpattern 108 may be formed of silicon (Si). In other embodiments, thesecond buffer pattern 106 may be formed of Si_(1-x)Ge_(x), and thechannel pattern 108 may be formed of Si_(1-y)Ge_(y) (where x>y). Instill other exemplary embodiments, the second buffer pattern 106 may beformed of In_(1-x)Ga_(x)As, and the channel pattern 108 may be formed ofIn_(1-y)Ga_(y)As (where x<y).

Alternatively, in exemplary embodiments in which the semiconductorcomponent is a P-type MOS (PMOS) field effect transistor, the secondbuffer pattern 106 may provide a compressive strain to the channelpattern 108. In some exemplary embodiments, the second buffer pattern106 may be formed of Si_(1-x)Ge_(x), and the channel pattern 108 may beformed of germanium (Ge). In other exemplary embodiments, the secondbuffer pattern 106 may be formed of Si_(1-z)Ge_(z), and the channelpattern 108 may be formed of Si_(1-w)Ge_(w) (where z<w). In still otherexemplary embodiments, the second buffer pattern 106 may be formed ofIn_(1-z)Ga_(z)As, and the channel pattern 108 may be formed ofIn_(1-w)Ga_(w)As (where z>w).

In exemplary embodiments in which the semiconductor component is theNMOS field effect transistor, the doped pattern 104 may be N-type. Insuch exemplary embodiments, the doped pattern 104 may provide extraelectrons to the channel pattern 108 when the NMOS field effecttransistor is turned-on. Alternatively, in exemplary embodiments inwhich the semiconductor component is the PMOS field effect transistor,the doped pattern 104 may be P-type. In such exemplary embodiments, thedoped pattern 104 may provide extra holes to the channel pattern 108when the PMOS field effect transistor is turned-on. That is, inexemplary embodiments in accordance with principles of inventiveconcepts the doped pattern 104 may provide the extra carriers (e.g.,electrons or holes) to the channel pattern 108, so electricalconductivity of the channel pattern 108 may be increased.

According to inventive concepts, the extra carriers may be provided tothe channel pattern 108 using the doped pattern 104 which is formed ofgraphene injected or doped with the impurity. In this manner, inaccordance with principles of inventive concepts, the electricalconductivity in the channel pattern 108 may be increased to improve anoperating characteristic of the field effect transistor. In addition,the doped pattern 104 may have a uniform thickness t of the one atomiclayer employing the two-dimensional crystal structure of the graphene,so a characteristic dispersion of the field effect transistor may beimproved. Furthermore, heat generated from the field effect transistorincluding the doped pattern 104 may be easily dissipated by a high heatconductivity property of the graphene.

FIGS. 2 to 5 are cross-sectional views corresponding to the lines I-I′and II-II′ of FIG. 1A to illustrate a method of forming a semiconductordevice according to a first exemplary embodiment in accordance withprinciples of inventive concepts. FIG. 6 is a cross-sectional viewcorresponding to the line II-II′ of FIG. 1A to illustrate a method offorming a semiconductor device according to a modified embodiment of afirst embodiment of the inventive concepts. FIGS. 7A, 7B, and 7C areconceptual diagrams illustrating a method of forming a graphene layer ona first buffer layer. FIGS. 8A, 8B, and 8C are conceptual diagramsillustrating a method of forming a second buffer layer on a dopedgraphene layer.

Referring to FIG. 2, a first buffer layer 122 may be formed on asubstrate 100. The first buffer layer 122 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound, forexample. In some exemplary embodiments, the first buffer layer 122 maybe formed by a selective epitaxial growth (SEG) process using thesubstrate 100 as a seed. In other exemplary embodiments, the firstbuffer layer 122 may be formed by a chemical vapor deposition (CVD)process or a molecular beam epitaxy process. A graphene layer 124 may beprovided on the first buffer layer 122. The graphene layer 124 may beformed on an additional support substrate and then may be provided onthe first buffer layer 122 by a transfer process. Hereinafter, anexample of the method of providing the graphene layer 124 onto the firstbuffer layer 122 in accordance with principles of inventive conceptswill be described in detail with reference to FIGS. 7A, 7B, and 7C.

Referring to FIG. 7A, a first support substrate 200 may be firstprovided. The first support substrate 200 may include, for example,silicon oxide. A metal catalyst layer 202 may be deposited on the firstsupport substrate 200. The metal catalyst layer 202 may be formed by,for example, a CVD process. The metal catalyst layer 202 may include atransition metal such as nickel (Ni), copper (Cu), and/or platinum (Pt),for example. The graphene layer 124 may be formed on the metal catalystlayer 202 by a CVD process. In an exemplary embodiment, a mixture gas ofmethane and hydrogen may be provided on the metal catalyst layer 202 ata high temperature of 1000° C., so carbon included in the mixture gasmay be adsorbed to the metal catalyst layer 202. Thereafter, carbonatoms included in the metal catalyst layer 202 may be crystallized on asurface of the metal catalyst layer 202 by a cooling process, so thegraphene layer 124 may be formed. In exemplary embodiments in accordancewith principles of inventive concepts graphene layer 124 may be providedonto the first buffer layer 122 by a transfer process that will bedescribed later.

Referring to FIG. 7B, an adhesive member 204 may be adhered to onesurface of the graphene layer 124. The adhesive member 204 may be, forexample, a thermal release tape. Next, a wet etching process may beperformed to remove the metal catalyst layer 202. In this manner, inaccordance with principles of inventive concepts, graphene layer 124 andthe adhesive member 204 adhered thereto may be separated from the firstsupport substrate 200.

Referring to FIGS. 2 and 7C, the graphene layer 124 adhered to theadhesive member 204 may be provided onto, or transferred to, the firstbuffer layer 122. The graphene layer 124 may be provided onto the firstbuffer layer 122 such that another surface (that is, the surface not incontact with adhesive member 204) of the graphene layer 124 may be incontact with a top surface of the first buffer layer 122. Subsequently,the adhesive member 204 may be separated from the graphene layer 124 bya thermal treatment process, so the graphene layer 124 may betransferred to the top surface of the first buffer layer 122.

Referring to FIG. 3, the graphene 124 may be doped with an impurity IMto form a doped graphene layer 125. If the doped graphene layer 125 hasan N-type, the impurity IM may include, for example, halogen atoms(e.g., nitrogen or fluorine). If the doped graphene layer 125 has aP-type, the impurity IM may include, for example, boron. A concentrationof the impurity IM in the doped graphene layer 125 may be higher than1×10⁶/cm² and equal to or lower than 1×10¹²/cm². Doping the graphenelayer 124 with the impurity IM may include exposing the graphene layer124 to an arc discharge. In such exemplary embodiments, the impurity IMmay be substituted for one or some of the carbon atoms of the graphenelayer 124 to form the doped graphene layer 125.

Referring to FIG. 4, a second buffer layer 126, a channel layer 128, anda barrier layer 132 may be sequentially formed on the doped graphenelayer 125. A method in accordance with principles of inventive conceptsof forming the second buffer layer 126 on the doped graphene layer 125will be described in detail with reference to FIGS. 8A, 8B, and 8C.

Referring to FIG. 8A, a second buffer layer 126 may be formed on asecond support substrate 300. The second support substrate 300 may be asemiconductor substrate formed of silicon, germanium, orsilicon-germanium or may be a SOI substrate, for example. The secondbuffer layer 126 may include the same material as the first buffer layer122 and may include silicon (Si), germanium (Ge), silicon-germanium(SiGe), or a III-V group compound, for example. According to anexemplary embodiment, the second buffer layer 126 may include the samematerial as the first buffer layer 122 and may have the same compositionratio as the first buffer layer 122. Alternatively, the second bufferlayer 126 may include the same material as the first buffer layer 122,but the composition ratio of the second buffer layer 126 may bedifferent from that of the first buffer layer 122. In an exemplaryembodiment, the second buffer layer 126 may be formed by a SEG processusing the second support substrate 300 as a seed. In another exemplaryembodiment, the second buffer layer 126 may be formed using a CVDprocess or a molecular beam epitaxy process.

The second buffer layer 126 formed on the second support substrate 300may be provided on the doped graphene layer 125. The second buffer layer126 may have a first surface being in contact with the second supportsubstrate 300 and a second surface opposite to the first surface. Thesecond surface of the second buffer layer 126 may face a top surface ofthe doped graphene layer 125.

Referring to FIG. 8B, the second buffer layer 126 and the second supportsubstrate 300 may be provided on the doped graphene layer 125 such thatthe second surface of the second buffer layer 126 may be in contact withthe top surface of the doped graphene layer 125. In exemplaryembodiments, the second buffer layer 126 may be adhered to the dopedgraphene layer 125 by pressure or heat. Hereinafter, a method ofremoving the second support substrate 300 from the second buffer layer126 will be described.

An ion implantation process may be performed on the substrate 100 toimplant hydrogen ions H⁺ into the second buffer layer 126. In thismanner, in accordance with principles of inventive concepts a bubblelayer may be formed in the second buffer layer 126 to define aninterface L at which the second buffer layer 126 can be physicallydivided. Second buffer layer 126 may be divided into an upper portion UPadjacent to the second support substrate 300 and a lower portion LPadjacent to the doped graphene layer 125 by interface L.

Referring to FIG. 8C, the second support substrate 300 and the upperportion UP of the second buffer layer 126 may be physically separatedand removed from the lower portion LP of the second buffer layer 126along interface L. Next, though not shown in the drawings, aplanarization process (e.g., a polishing process or an etch-backprocess) may be performed on the lower portion LP of the second bufferlayer 126. In this manner, in accordance with principles of inventiveconcepts, the lower portion LP of the second buffer layer 126 remainingon the doped graphene layer 125 may have a flat top surface and apredetermined thickness in a direction perpendicular to a top surface ofthe substrate 100. Hereinafter, the remaining lower portion LP of thesecond buffer layer 126 may be referred to as a second buffer layer 126.

Referring again to FIG. 4, the channel layer 128 and the barrier layer132 may be sequentially formed on the second buffer layer 126.

The channel layer 128 may include a material of which an energy band gapis smaller than that of the second buffer layer 126. In some exemplaryembodiments, the channel layer 128 may include a material of which anenergy band gap is smaller than those of the first and second bufferlayers 122 and 126. The channel layer 128 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound, forexample. The channel layer 128 may receive a compressive strain or atensile strain from the second buffer layer 126. In some exemplaryembodiments, the channel layer 128 may be formed using a SEG process, aCVD process, or a molecular beam epitaxy process.

The barrier layer 132 may include a material of which an energy band gapis greater than that of the channel layer 128. That is, in exemplaryembodiments in accordance with principles of inventive concepts, thechannel layer 128 may include the material of which the energy band gapis smaller than those of the barrier layer 132 and the second bufferlayer 126. As a result, in accordance with principles of inventiveconcepts, the channel layer 128 may have a quantum well structure. Thebarrier layer 132 may include silicon (Si), germanium (Ge),silicon-germanium (SiGe), or a III-V group compound. In other exemplaryembodiments, the barrier layer 132 may be omitted.

Referring to FIG. 5, the barrier layer 132, the channel layer 128, thesecond buffer layer 126, the doped graphene layer 125, and the firstbuffer layer 122 may be sequentially patterned to form an active patternAP on the substrate 100. An upper portion of the substrate 100 may berecessed during the patterning process. In exemplary embodiments onaccordance with principles of inventive concepts, active pattern AP mayinclude a first buffer pattern 102, a doped pattern 104, a second bufferpattern 106, a channel pattern 108, and a barrier pattern 112 which aresequentially stacked on the substrate 100.

A device isolation layer ST covering sidewalls of the active pattern APmay be formed on the substrate 100. Forming the device isolation layerST may include forming an insulating layer covering the active patternAP on the substrate 100, and planarizing the insulating layer until atop surface of the active pattern AP is exposed. The insulating layermay include at least one of an oxide layer, a nitride layer, or anoxynitride layer, for example. In some exemplary embodiments, thesidewalls of the active pattern AP may not be exposed by the deviceisolation layer ST, as illustrated in FIG. 5. In other embodiments, theactive pattern AP may include an upper portion (hereinafter, referred toas ‘an active fin AF’) exposed by the device isolation layer ST, asillustrated in FIG. 6. That is, in accordance with principles ofinventive concepts, upper portions of both sidewalls of the activepattern AP may be exposed by the device isolation layer ST. In thiscase, the planarization process may be performed until the deviceisolation layer ST has a desired thickness on the substrate 100. As aresult, in exemplary embodiments in accordance with principles ofinventive concepts, a height of a top surface STu of the deviceisolation layer ST may be lower than a height of a bottom surface 104Lof the doped pattern 104.

Referring again to FIGS. 1A, 1B, and 1C, a gate electrode GEintersecting the active pattern AP may be formed on the substrate 100.In an exemplary embodiment, the gate electrode GE may cover the topsurface of the active pattern AP and a top surface of the deviceisolation layer ST, as illustrated in FIG. 1C. In another exemplaryembodiment, the gate electrode GE may cover the top surface and theexposed sidewalls of the active pattern AP and may extend onto the topsurface of the device isolation layer ST, as illustrated in FIG. 1D.

A gate insulating pattern GI may be formed between the gate electrode GEand the active pattern AP, and a capping pattern CAP may be formed on atop surface of the gate electrode GE. According to an exemplaryembodiment, forming the gate insulating pattern GI, the gate electrodeGE, and the capping pattern CAP may include sequentially forming a gateinsulating layer, a gate electrode layer, and a capping layer on thesubstrate 100, and successively patterning the capping layer, the gateelectrode layer, and the gate insulating layer to form the cappingpattern CAP, the gate electrode GE, and the gate insulating pattern GI.The gate insulating pattern GI may include at least one of a high-kdielectric layer (e.g., a hafnium oxide layer, a hafnium silicate layer,a zirconium oxide layer, or a zirconium silicate layer) or a siliconoxide layer, for example. The gate electrode GE may include at least oneof doped silicon, a metal, or a conductive metal nitride (e.g., titaniumnitride (TiN) or tantalum nitride (TaN)). The capping pattern CAP mayinclude, for example, a nitride layer such as a silicon nitride layer.

Subsequently, gate spacers GS may be formed on both sidewalls of thegate electrode GE. In some exemplary embodiments, a spacer layer may beformed on the substrate 100 having the gate insulating pattern GI, thegate electrode GE, and the capping pattern CAP, and the spacer layer maybe anisotropically etched to form the gate spacers GS. The gate spacersGS may include a nitride layer such as a silicon nitride layer, forexample. Thereafter, source/drain regions 110 may be formed in theactive pattern AP at both sides of the gate electrode GE.

FIG. 9A is a plan view illustrating a semiconductor device according toa second exemplary embodiment in accordance with principles of inventiveconcepts. FIGS. 9B, 9C, and 9D are cross-sectional views taken alonglines I-I′, II-II′, and III-III′ of FIG. 9A, respectively. FIG. 9E is across-sectional view corresponding to the line III-III′ of FIG. 9A toillustrate a semiconductor device according to a modified embodiment ofa second embodiment of the inventive concepts. In the present exemplaryembodiment, the same elements as described in the first embodiment ofFIGS. 1A to 1C will be indicated by the same reference numerals or thesame reference designators. For the purpose of ease and convenience inexplanation, the descriptions to the same elements as in the firstembodiment will be omitted or mentioned only briefly here.

Referring to FIGS. 9A, 9B, 9C, and 9D, a device isolation layer STdefining a plurality of active patterns AP1 and AP2 may be provided on asubstrate 100. The active patterns AP1 and AP2 may include a firstactive pattern AP1 and a second active pattern AP2 that are spaced apartfrom each other with the device isolation layer ST interposedtherebetween. Each of the active patterns AP1 and AP2 may have a barshape extending in a first direction D1. The active patterns AP1 and AP2may be spaced apart from each other in a second direction D2intersecting the first direction D1.

Each of the active patterns AP1 and AP2 may include a first bufferpattern 102 on the substrate 100, a channel pattern 108 on the firstbuffer pattern 102, and a second buffer pattern 106 between the firstbuffer pattern 102 and the channel pattern 108. In an exemplaryembodiment, each of the active patterns AP1 and AP2 may further includea barrier pattern 112 disposed on the channel pattern 108. In suchexemplary embodiments, the channel pattern 108 may be disposed betweenthe barrier pattern 112 and the second buffer pattern 106.

According to the present exemplary embodiment, the first active patternAP1 may include a first doped pattern 104 a disposed between the firstand second buffer patterns 102 and 106 of the first active pattern AP1,and the second active pattern AP2 may include a second doped pattern 104b disposed between the first and second buffer patterns 102 and 106 ofthe second active pattern AP2.

Each of the first and second doped patterns 104 a and 104 b may includegraphene that is injected or doped with an impurity and may have acrystal structure formed by substituting the impurity for one or some ofcarbon atoms of the graphene. Each of the first and second dopedpatterns 104 a and 104 b may have a thickness t of one atomic layeremploying a two-dimensional crystal structure of the graphene. Thethickness t of the first doped pattern 104 a may be substantially equalto the thickness t of the second doped pattern 104 b.

The first doped pattern 104 a and the second doped pattern 104 b mayhave different conductivity types from each other. For example, if thefirst doped pattern 104 a has a P-type, the second doped pattern 104 bhas an N-type. If the first doped pattern 104 a has the P-type, theimpurity of the first doped pattern 104 a may be, for example, boron. Ifthe second doped pattern 104 b has the N-type, the impurity of thesecond doped pattern 104 b may be, for example, halogen atoms such asnitrogen or fluorine.

In a cross-sectional view, the first doped pattern 104 a may be moreadjacent, or closer, to the channel pattern 108 of the first activepattern AP1 than to the substrate 100. The first doped pattern 104 a mayprovide extra carriers to the channel pattern 108 of the first activepattern AP1. If the first doped pattern 104 a has the P-type, the firstdoped pattern 104 a may provide extra holes to the channel pattern 108of the first active pattern AP1, for example. Similarly, the seconddoped pattern 104 b may be more adjacent, or closer, to the channelpattern 108 of the second active pattern AP2 than to the substrate 100.The second doped pattern 104 b may provide extra carriers to the channelpattern 108 of the second active pattern AP2. If the second dopedpattern 104 b has the N-type, the second doped pattern 104 b may provideextra electrons to the channel pattern 108 of the second active patternAP2, for example.

According to the present exemplary embodiment, the channel pattern 108of the first active pattern AP1 may be formed of the same material asthe channel pattern 108 of the second active pattern AP2. In someexemplary embodiments, the channel patterns 108 of the first and secondactive patterns AP1 and AP2 may include a III-group antimonide (Sb)compound. The III-group antimonide may include indium-gallium antimonide(InGaSb) or indium antimonide (InSb), for example.

The first buffer pattern 102 of the first active pattern AP1 may beformed of the same material as the first buffer pattern 102 of thesecond active pattern AP2. The second buffer pattern 106 of the firstactive pattern AP1 may be formed of the same material as the secondbuffer pattern 106 of the second active pattern AP2. The barrier pattern112 of the first active pattern AP1 may be formed of the same materialas the barrier pattern 112 of the second active pattern AP2.

In each of the active patterns AP1 and AP2, the channel pattern 108 mayinclude a material of which an energy band gap is smaller than those ofthe second buffer pattern 106 and the barrier pattern 112. As a result,in accordance with principles of inventive concepts, the channel pattern108 may have a quantum well structure. In other exemplary embodiments,the barrier pattern 112 may be omitted in each of the active patternsAP1 and AP2.

According to an exemplary embodiment, both sidewalls of each of theactive patterns AP1 and AP2 may not be exposed by the device isolationlayer ST, as illustrated in FIG. 9D. Alternatively, each of the activepatterns AP1 and AP2 may have an upper portion (e.g., an active fin AF)exposed by the device isolation layer ST, as illustrated in FIG. 9E.That is, in accordance with principles of inventive concepts, upperportions of the both sidewalls of each of the active patterns AP1 andAP2 may be exposed by the device isolation layer ST. In suchembodiments, a height of a top surface STu of the device isolation layerST may be lower than a height of a bottom surface 104L of each of thefirst and second doped patterns 104 a and 104 b.

A gate electrode GE may be provided to intersect the active patterns AP1and AP2. According to an exemplary embodiment, one gate electrode GE mayintersect the plurality of active patterns AP1 and AP2, as illustratedin FIG. 9A. Alternatively, unlike FIG. 9A, a plurality of gateelectrodes GE may be provided to intersect the plurality of activepatterns AP1 and AP2, respectively.

The gate electrode GE may be provided on the active patterns AP1 and AP2and may extend in the second direction D2. According to an exemplaryembodiment, the gate electrode GE may cover top surfaces of the activepatterns AP1 and AP2 and a top surface of the device isolation layer ST,as illustrated in FIG. 9D. According to another exemplary embodiment,the gate electrode GE may cover the top surfaces and the exposedsidewalls of the active patterns AP1 and AP2 and may extend onto the topsurface of the device isolation layer ST, as illustrated in FIG. 9E. Agate insulating pattern GI may be provided between the gate electrode GEand the active patterns AP1 and AP2. The gate insulating pattern GI mayextend along a bottom surface of the gate electrode GE in the seconddirection D2. A capping pattern CAP may be provided on a top surface ofthe gate electrode GE, and gate spacers GS may be provided on bothsidewalls of the gate electrode GE. Source/drain regions 110 may beprovided in the active patterns AP1 and AP2 at both sides of the gateelectrode GE. As a result, in accordance with principles of inventiveconcepts, a first transistor TR1 and a second transistor TR2 may beprovided on the substrate 100. The first transistor TR1 may include thefirst active pattern AP1, and the second transistor TR2 may include thesecond active pattern AP2.

The first transistor TR1 and the second transistor TR2 may be fieldeffect transistors that have different conductivity types from eachother. In some exemplary embodiments, the first transistor TR1 may be aPMOS field effect transistor, and the second transistor TR2 may be anNMOS field effect transistor. According to the present exemplaryembodiment, the channel pattern 108 of the first transistor TR1 may beformed of the same material as the channel pattern 108 of the secondtransistor TR2. The conductivity types of the first and secondtransistors TR1 and TR2 may be determined depending on the conductivitytypes of the first and second doped patterns 104 a and 104 b. That is,in exemplary embodiments in accordance with principles of inventiveconcepts, if the first doped pattern 104 a has the P-type, the firsttransistor TR1 may be the PMOS field effect transistor and if the seconddoped pattern 104 b has the N-type, the second transistor TR2 may be theNMOS field effect transistor. In such exemplary embodiments, the firstdoped pattern 104 a may provide the extra holes to the channel pattern108 of the first transistor TR1, and the second doped pattern 104 b mayprovide the extra electrons to the channel pattern 108 of the secondtransistor TR2.

According to the present exemplary embodiment, the first and secondtransistors TR1 and TR2, which have the same channel material but havedifferent conductivity types, may be realized using the first and seconddoped patterns 104 a and 104 b, which have different conductivity typesfrom each other.

FIGS. 10A to 13A are plan views illustrating an exemplary method offorming a semiconductor device according to a second embodiment of theinventive concepts in accordance with principles of inventive concepts.FIGS. 10B to 13B are cross-sectional views taken along lines I-I′,II-II′, and III-III′ of FIGS. 10A to 13A, respectively. FIG. 14 is across-sectional view corresponding to the line III-III′ of FIG. 13A toillustrate a method of forming a semiconductor device according to amodified embodiment of a second exemplary embodiment in accordance withprinciples of inventive concepts. In the present exemplary embodiment,the same elements as described in the formation method according to thefirst embodiment of FIGS. 2 to 5 will be indicated by the same referencenumerals or the same reference designators. For the purpose of ease andconvenience in explanation, the descriptions to the same elements as inthe formation method of the first embodiment will be omitted or onlybriefly described.

A first buffer layer 122 may be first formed on a substrate 100, asdescribed with reference to FIG. 2. The first buffer layer 122 mayinclude silicon (Si), germanium (Ge), silicon-germanium (SiGe), or aIII-V group compound. A graphene layer 124 may be provided on the firstbuffer layer 122. As described with reference to FIGS. 7A, 7B, and 7C,the graphene layer 124 may be formed on the first support substrate 200and may be then provided onto, or formed on, the first buffer layer 122by means of a transfer process.

Referring to FIGS. 10A and 10B, a first mask layer M1 may be formed onthe graphene layer 124. The first mask layer M1 may be, for example, aphotoresist layer. The first mask layer M1 may have a first opening 140that exposes the graphene layer 124. The first opening 140 may extend ina first direction D1 and may expose a portion of a top surface of thegraphene layer 124. The portion of the graphene layer 124 exposed by thefirst opening 140 may be doped with an impurity IM using the first masklayer M1 as a doping mask. In this manner, a first doped region r1 maybe formed in the graphene layer 124. If the first doped region r1 has anN-type, the impurity IM may include, for example, halogen atoms such asnitrogen or fluorine. If the first doped region r1 has a P-type, theimpurity IM may include, for example, boron. In some exemplaryembodiments, doping the exposed portion of the graphene layer 124 withthe impurity IM may include exposing the exposed portion of the graphenelayer 124 to an arc discharge in a gas atmosphere including the impurityIM. In such exemplary embodiments, some of carbon atoms of the exposedportion of the graphene layer 124 may be replaced with the impurity IMto form the first doped region r1.

Referring to FIGS. 11A and 11B, the first mask layer M1 may be removedafter the formation of the first doped region r1. The first mask layerM1 may be removed by, for example, an ashing process and/or a stripprocess. Next, a second mask layer M2, which may be a photoresist layer,may be formed on the graphene layer 124 including the first doped regionr1. The second mask layer M2 may have a second opening 142 that exposethe graphene 124. The second opening 142 may extend in the firstdirection D1 and may expose a portion of the top surface of the graphenelayer 124. The second opening 142 may be spaced apart from the firstdoped region r1 in a second direction D2 intersecting the firstdirection D1 when viewed from a plan view.

The portion of the graphene layer 124 exposed by the second opening 142may be doped with an impurity IM using the second mask layer M2 as adoping mask. In this manner, in accordance with principles of inventiveconcepts, a second doped region r2 may be formed in the graphene layer124. The second doped region r2 may be spaced apart from the first dopedregion r1 in the second direction D2. If the second doped region r2 hasan N-type, the impurity IM may include, for example, halogen atoms suchas nitrogen or fluorine. If the second doped region r2 has an P-type,the impurity IM may include, for example, boron. The conductivity typeof the second doped region r2 may be different from that of the firstdoped region r1. That is, in accordance with principles of inventiveconcepts, if the first doped region r1 has the P-type, the second dopedregion r2 may be N-type. Doping the portion, exposed by the secondopening 142, of the graphene layer 124 with the impurity IM may be asdescribed with reference to FIGS. 10A and 10B.

Referring to FIGS. 12A and 12B, the second mask layer M2 may be removedafter the formation of the second doped region r2. For example, thesecond mask layer M2 may be removed by an ashing process and/or a stripprocess. A second buffer layer 126, a channel layer 128, and a barrierlayer 132 may be sequentially formed on the graphene layer 124 includingthe first and second doped regions r1 and r2.

The second buffer layer 126 may include the same material as the firstbuffer layer 122 and may include silicon (Si), germanium (Ge),silicon-germanium (SiGe), or a III-V group compound, for example.According to an exemplary embodiment, the second buffer layer 126 mayinclude the same material as the first buffer layer 122 and may have thesame composition ratio as the first buffer layer 122. Alternatively, thesecond buffer layer 126 may include the same material as the firstbuffer layer 122, but the composition ratio of the second buffer layer126 may be different from that of the first buffer layer 122. The secondbuffer layer 126 may be formed as described with reference to FIGS. 8A,8B, and 8C.

The channel layer 128 may include a material of which an energy band gapis smaller than that of the second buffer layer 126. In someembodiments, the channel layer 128 may include a material of which anenergy band gap is smaller than those of the first and second bufferlayers 122 and 126. The channel layer 128 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound.

The barrier layer 132 may include a material of which an energy band gapis greater than that of the channel layer 128. That is, in exemplaryembodiments in accordance with principles of inventive concepts, thechannel layer 128 may include the material of which the energy band gapis smaller than those of the barrier layer 132 and the second bufferlayer 126 and, as a result , the channel layer 128 may have a quantumwell structure. The barrier layer 132 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound. Inother exemplary embodiments, the barrier layer 132 may be omitted.

The channel layer 128 and the barrier layer 132 may be formed asdescribed with reference to FIG. 4.

Referring to FIGS. 13A and 13B, the barrier layer 132, the channel layer128, the second buffer layer 126, the graphene layer 124 including thefirst and second doped regions r1 and r2, and the first buffer layer 122may be sequentially patterned to form active patterns AP1 and AP2 on thesubstrate 100. An upper portion of the substrate 100 may be recessedduring the patterning process. During the patterning process, thegraphene layer 124 may be patterned to form a first doped pattern 104 aincluding the first doped region r1 and a second doped pattern 104 bincluding the second doped region r2, for example. The active patternsAP1 and AP2 may include a first active pattern AP1, including the firstdoped pattern 104 a, and a second active pattern AP2, including thesecond doped pattern 104 b.

Each of the active patterns AP1 and AP2 may include a first bufferpattern 102, a second buffer pattern 106, a channel pattern 108, and abarrier pattern 112, which are sequentially stacked on the substrate100. According to the present exemplary embodiment, the first activepattern AP1 may include the first doped pattern 104 a disposed betweenthe first and second buffer patterns 102 and 106 of the first activepattern AP1, and the second active pattern AP2 may include the seconddoped pattern 104 b disposed between the first and second bufferpatterns 102 and 106 of the second active pattern AP2.

A device isolation layer ST covering sidewalls of the active patternsAP1 and AP2 may be formed on the substrate 100. According to anexemplary embodiment, the sidewalls of the active patterns AP1 and AP2may not be exposed by the device isolation layer ST, as illustrated inFIG. 13B. According to another exemplary embodiment, each of the activepatterns AP1 and AP2 may include an upper portion (e.g., an active finAF) exposed by the device isolation layer ST, as illustrated in FIG. 14.In such exemplary embodiments, a height of a top surface STu of thedevice isolation layer ST may be lower than a height of a bottom surface104L of each of the first and second doped patterns 104 a and 104 b.

Referring again to FIGS. 9A, 9B, 9C, and 9D, a gate electrode GEintersecting the active patterns AP1 and AP2 may be formed on thesubstrate 100. The gate electrode GE may be provided on the activepatterns AP1 and AP2 and may extend in the second direction D2. In anexemplary embodiment, the gate electrode GE may cover the top surfacesof the active patterns AP1 and AP2 and the top surface of the deviceisolation layer ST, as illustrated in FIG. 9D. In another exemplaryembodiment, the gate electrode GE may cover the top surfaces and theexposed sidewalls of the active patterns AP1 and AP2 and may extend ontothe top surface of the device isolation layer ST, as illustrated in FIG.9E. A gate insulating pattern GI may be formed between the gateelectrode GE and the active patterns AP1 and AP2. A capping pattern CAPmay be formed on a top surface of the gate electrode GE, and gatespacers GS may be formed on both sidewalls of the gate electrode GE. Inexemplary embodiments in accordance with principles of inventiveconcepts, the gate insulating pattern GI, the gate electrode GE, thecapping pattern CAP, and the gate spacers GS may be formed by thesubstantially same method as described in the first embodiment withreference to FIGS. 1A to 1C. Thereafter, source/drain regions 110 may beformed in the active patterns AP1 and AP2 at both sides of the gateelectrode GE.

FIG. 15A is a plan view illustrating a semiconductor device according toa third exemplary embodiment in accordance with principles of inventiveconcepts. FIGS. 15B, 15C, 15D, and 15E are cross-sectional views takenalong lines I-I′, II-II′, III-III′, and IV-IV′ of FIG. 15A,respectively. FIG. 15F is a cross-sectional view corresponding to theline IV-IV′ of FIG. 15A to illustrate a semiconductor device accordingto a modified embodiment of a third exemplary embodiment in accordancewith principles of inventive concepts. In the present exemplaryembodiment, the same elements as described in the first embodiment ofFIGS. 1A to 1C will be indicated by the same reference numerals or thesame reference designators. For the purpose of ease and convenience inexplanation, descriptions of the same elements as in the firstembodiment will be omitted or only briefly described.

Referring to FIGS. 15A, 15B, 15C, 15D, and 15E, a device isolation layerST defining a plurality of active patterns AP1, AP2, and AP3 may beprovided on a substrate 100. The active patterns AP1, AP2, and AP3 mayinclude a first active pattern AP1, a second active pattern AP2, and athird active pattern AP3 that are spaced apart from each other with thedevice isolation layer ST interposed therebetween. Each of the activepatterns AP1, AP2, and AP3 may have a bar shape extending in a firstdirection D1. The active patterns AP1, AP2, and AP3 may be spaced apartfrom each other in a second direction D2 intersecting the firstdirection D1.

Each of the active patterns AP1, AP2, and AP3 may include a first bufferpattern 102 on the substrate 100, a channel pattern 108 on the firstbuffer pattern 102, and a second buffer pattern 106 between the firstbuffer pattern 102 and the channel pattern 108. According to anexemplary embodiment, each of the active patterns AP1, AP2, and AP3 mayfurther include a barrier pattern 112 disposed on the channel pattern108. In such exemplary embodiments, the channel pattern 108 may bedisposed between the barrier pattern 112 and the second buffer pattern106.

According to the present exemplary embodiment, the first active patternAP1 may include a first doped pattern 104 a disposed between the firstand second buffer patterns 102 and 106 of the first active pattern AP1,and the second active pattern AP2 may include a second doped pattern 104b disposed between the first and second buffer patterns 102 and 106 ofthe second active pattern AP2. The third active pattern AP3 may includea third doped pattern 104 c disposed between the first and second bufferpatterns 102 and 106 of the third active pattern AP3.

Each of the first to third doped patterns 104 a, 104 b, and 104 c mayinclude graphene that is injected or doped with an impurity and may havea crystal structure formed by substituting the impurity for one or someof carbon atoms of the graphene. Each of the first to third dopedpatterns 104 a, 104 b, and 104 c may have a thickness t of one atomiclayer employing a two-dimensional crystal structure of the graphene. Thethicknesses t of the first, second, and third doped patterns 104 a, 104b, and 104 c may be substantially equal to each other.

According to the present exemplary embodiment, the first to third dopedpatterns 104 a, 104 b, and 104 c may have the same conductivity type,but impurity concentrations of the first to third doped patterns 104 a,104 b, and 104 c may be different from each other. In some embodiments,the first to third doped patterns 104 a, 104 b, and 104 c may have aP-type, and the impurity concentrations of the first to third dopedpatterns 104 a, 104 b, and 104 c may be different from each other. Insuch exemplary embodiments, the impurity may include, for example,boron. In other exemplary embodiments, the first to third doped patterns104 a, 104 b, and 104 c may have an N-type, and the impurityconcentrations of the first to third doped patterns 104 a, 104 b, and104 c may be different from each other. In such exemplary embodiments,the impurity may include, for example, halogen atoms such as nitrogen orfluorine.

In a cross-sectional view, each of the first to third doped patterns 104a, 104 b, and 104 c may be more adjacent, or closer, to the channelpattern 108 of each of the first to third active patterns AP1, AP2, andAP3 than to the substrate 100. Each of the first to third doped patterns104 a, 104 b, and 104 c may provide extra carriers to the channelpattern 108 of each of the first to third active patterns AP1, AP2, andAP3. In an exemplary embodiment, if the first to third doped patterns104 a, 104 b, and 104 c are P-type, each of the first to third dopedpatterns 104 a, 104 b, and 104 c may provide extra holes to the channelpattern 108 of each of the first to third active patterns AP1, AP2, andAP3. In another exemplary embodiment, if the first to third dopedpatterns 104 a, 104 b, and 104 c are N-type, each of the first to thirddoped patterns 104 a, 104 b, and 104 c may provide extra electrons tothe channel pattern 108 of each of the first to third active patternsAP1, AP2, and AP3.

The channel patterns 108 of the first to third active patterns AP1, AP2,and AP3 may be formed of the same material and may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound, forexample.

The first buffer patterns 102 of the first to third active patterns AP1,AP2, and AP3 may be formed of the same material, and the second bufferpatterns 106 of the first to third active patterns AP1, AP2, and AP3 maybe formed of the same material. In addition, the barrier patterns 112 ofthe first to third active patterns AP1, AP2, and AP3 may be formed ofthe same material.

In exemplary embodiments in accordance with principles of inventiveconcepts, each of the first to third active patterns AP1, AP2, and AP3,the channel pattern 108 may include a material of which an energy bandgap is smaller than those of the second buffer pattern 106 and thebarrier pattern 112. As a result, the channel pattern 108 may have aquantum well structure. In other exemplary embodiments, the barrierpattern 112 may be omitted in each of the active patterns AP1, AP2, andAP3.

According to an exemplary embodiment, both sidewalls of each of theactive patterns AP1, AP2, and AP3 may not be exposed by the deviceisolation layer ST, as illustrated in FIG. 15E. Alternatively, each ofthe active patterns AP1, AP2, and AP3 may have an upper portion (e.g.,an active fin AF) exposed by the device isolation layer ST, asillustrated in FIG. 15F. That is, in exemplary embodiments in accordancewith principles of inventive concepts, upper portions of the bothsidewalls of each of the active patterns AP1, AP2, and AP3 may beexposed by the device isolation layer ST. In such exemplary embodiments,a height of a top surface STu of the device isolation layer ST may belower than a height of a bottom surface 104L of each of the first tothird doped patterns 104 a, 104 b, and 104 c.

Gate electrodes GE may be provided to intersect the active patterns AP1,AP2, and AP3, respectively. According to an exemplary embodiment, aplurality of gate electrodes GE may be provided to intersect theplurality of active patterns AP1, AP2, and AP3, respectively, asillustrated in FIG. 15A. Alternatively, unlike FIG. 15A, one gateelectrode GE intersecting the plurality of active patterns AP1, AP2, andAP3 may be provided on the substrate 100.

The gate electrodes GE may be provided on the active patterns AP1, AP2,and AP3 and may extend in the second direction D2. According to anexemplary embodiment, the gate electrodes GE may cover top surfaces ofthe active patterns AP1, AP2, and AP3 and a top surface of the deviceisolation layer ST, as illustrated in FIG. 15E. According to anotherexemplary embodiment, each of the gate electrodes GE may cover the topsurface and the exposed sidewalls of each of the active patterns AP1,AP2, and AP3 and may extend onto the top surface of the device isolationlayer ST, as illustrated in FIG. 15F. A gate insulating pattern GI maybe provided between each of the gate electrodes GE and each of theactive patterns AP1, AP2, and AP3. The gate insulating pattern GI mayextend along a bottom surface of each of the gate electrodes GE in thesecond direction D2. A capping pattern CAP may be provided, or formed,on a top surface of each of the gate electrodes GE, and gate spacers GSmay be provided on both sidewalls of each of the gate electrodes GE.Source/drain regions 110 may be provided in the active patterns AP1,AP2, and AP3 at both sides of each of the gate electrodes GE. As aresult, a first transistor TR1, a second transistor TR2, and a thirdtransistor TR3 may be realized, or implemented, on the substrate 100.The first transistor TR1 may include the first active pattern AP1, andthe second transistor TR2 may include the second active pattern AP2. Thethird transistor TR3 may include the third active pattern AP3.

The first, second, and third transistors TR1, TR2, and TR3 may be fieldeffect transistors that have the same conductivity type but havedifferent threshold voltages from each other. In some exemplaryembodiments, the first to third transistors TR1, TR2, and the TR3 may bePMOS field effect transistors having different threshold voltages fromeach other or NMOS field effect transistors having different thresholdvoltages from each other. According to the present exemplary embodiment,the first to third doped patterns 104 a, 104 b, and 104 c may have thesame conductivity type but the impurity concentration of the first tothird doped patterns 104 a, 104 b, and 104 c may be different from eachother. As a result, the first to third transistors TR1, TR2, and TR3respectively including the first to third doped patterns 104 a, 104 b,and 104 c may have the same conductivity type but may have the differentthreshold voltages from each other.

FIGS. 16A to 20A are plan views illustrating a method of forming asemiconductor device according to a third exemplary embodiment inaccordance with principles of inventive concepts. FIGS. 16B to 20B arecross-sectional views taken along lines I-I′ and II-II′ of FIGS. 16A to20A, respectively. FIGS. 16C to 20C are cross-sectional views takenalong lines III-III′ and IV-IV′ of FIGS. 16A to 20A, respectively. FIG.21 is a cross-sectional view corresponding to the line IV-IV′ of FIG.20A to illustrate a method in accordance with principles of inventiveconcepts of forming a semiconductor device according to a modifiedembodiment of a third embodiment of the inventive concepts. In thepresent exemplary embodiment, the same elements as described in theformation method according to the first embodiment of FIGS. 2 to 5 willbe indicated by the same reference numerals or the same referencedesignators. For the purpose of ease and convenience in explanation, thedescriptions to the same elements as in the formation method of thefirst embodiment will be omitted or only briefly described.

A first buffer layer 122 may be first formed on a substrate 100, asdescribed with reference to FIG. 2. The first buffer layer 122 mayinclude silicon (Si), germanium (Ge), silicon-germanium (SiGe), or aIII-V group compound. A graphene layer 124 may be provided on the firstbuffer layer 122. As described with reference to FIGS. 7A, 7B, and 7C,the graphene layer 124 may be formed on the first support substrate 200and may be then provided onto, formed on, or transferred to the firstbuffer layer 122 by means of the transfer process.

Referring to FIGS. 16A, 16B, and 16C, a first mask layer M1 may beformed on the graphene layer 124. The first mask layer M1 may be, forexample, a photoresist layer. The first mask layer M1 may have a firstopening 140 that exposes the graphene layer 124. The first opening 140may extend in a first direction D1 and may expose a portion of a topsurface of the graphene layer 124. The portion of the graphene layer 124exposed by the first opening 140 may be doped with an impurity IM usingthe first mask layer M1 as a doping mask. In this manner, a first dopedregion r1 may be formed in the graphene layer 124. If the first dopedregion r1 has an N-type, the impurity IM may include, for example,halogen atoms such as nitrogen or fluorine. If the first doped region r1has a P-type, the impurity IM may include, for example, boron. In someexemplary embodiments, doping the exposed portion of the graphene layer124 with the impurity IM may include exposing the exposed portion of thegraphene layer 124 to an arc discharge in a gas atmosphere including theimpurity IM. In such exemplary embodiments, the impurity IM may besubstituted for one or some of carbon atoms of the exposed portion ofthe graphene layer 124 to form the first doped region r1.

Referring to FIGS. 17A, 17B, and 17C, the first mask layer M1 may beremoved after the formation of the first doped region r1. The first masklayer M1 may be removed by, for example, an ashing process and/or astrip process. Next, a second mask layer M2 may be formed on thegraphene layer 124 including the first doped region r1. The second masklayer M2 may be a photoresist layer, for example. The second mask layerM2 may have a second opening 142 that exposes the graphene 124. Thesecond opening 142 may extend in the first direction D1 and may expose aportion of the top surface of the graphene layer 124. The second opening142 may be spaced apart from the first doped region r1 in a seconddirection D2 intersecting the first direction D1 when viewed from a planview.

The portion of the graphene layer 124 exposed by the second opening 142may be doped with an impurity IM using the second mask layer M2 as adoping mask. In such exemplary embodiments, a second doped region r2 maybe formed in the graphene layer 124. The second doped region r2 may bespaced apart from the first doped region r1 in the second direction D2.If the second doped region r2 is N-type, the impurity IM may include,for example, halogen atoms such as nitrogen or fluorine. If the seconddoped region r2 is P-type, the impurity IM may include, for example,boron. In exemplary embodiments in accordance with principles ofinventive concepts, second doped region r2 may have the sameconductivity type as the first doped region r1, but an impurityconcentration of the second doped region r2 may be different from animpurity concentration of the first doped region r1. Doping the portion,exposed by the second opening 142, of the graphene layer 124 with theimpurity IM may be the same as described with reference to FIGS. 16A,16B, and 16C, for example.

Referring to FIGS. 18A, 18B, and 18C, the second mask layer M2 may beremoved after the formation of the second doped region r2. For example,the second mask layer M2 may be removed by an ashing process and/or astrip process. Thereafter, a third mask layer M3 may be formed on thegraphene layer 124 including the first and second doped regions r1 andr2. The third mask layer M3 may be, for example, a photoresist layer.The third mask layer M3 may include a third opening 144 that exposes thegraphene layer 124. The third opening 144 may extend in the firstdirection D1 and may be spaced apart from the first and second doperegions r1 and r2 in the second direction D2 when viewed from a planview.

The portion of the graphene layer 124 exposed by the third opening 144may be doped with an impurity IM using the third mask layer M3 as adoping mask. In this manner, a third doped region r3 may be formed inthe graphene layer 124. The third doped region r3 may be spaced apartfrom the first doped region r1 and the second doped region r2 in thesecond direction D2. That is, in exemplary embodiments in accordancewith principles of inventive concepts, the first doped region r1, thesecond doped region r2, and the third doped region r3 may be arrangedalong the second direction D2. If the third doped region r3 is N-type,the impurity IM may include, for example, halogen atoms such as nitrogenor fluorine. If the third doped region r3 is P-type, the impurity IM mayinclude, for example, boron. The third doped region r3 may have the sameconductivity type as the first doped region r1 and the second dopedregion r2. An impurity concentration of the third doped region r3 may bedifferent from the impurity concentrations of the first and second dopedregions r1 and r2. That is, in exemplary embodiments in accordance withprinciples of inventive concepts, the impurity concentrations of thefirst, second, and third doped regions r1, r2, and r3 may be differentfrom each other. Doping the portion, exposed by the third opening 144,of the graphene layer 124 with the impurity IM may be the same asdescribed with reference to FIGS. 16A, 16B, and 16C.

Referring to FIGS. 19A, 19B, and 19C, the third mask layer M3 may beremoved after the formation of the third doped region r3. For example,the third mask layer M3 may be removed by an ashing process and/or astrip process. A second buffer layer 126, a channel layer 128, and abarrier layer 132 may be sequentially formed on the graphene layer 124including the first, second, and third doped regions r1, r2, and r3.

The second buffer layer 126 may include the same material as the firstbuffer layer 122. The second buffer layer 126 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound, forexample. According to an exemplary embodiment, the second buffer layer126 may include the same material as the first buffer layer 122 and mayhave the same composition ratio as the first buffer layer 122.Alternatively, the second buffer layer 126 may include the same materialas the first buffer layer 122, but the composition ratio of the secondbuffer layer 126 may be different from that of the first buffer layer122. The second buffer layer 126 may be formed as described withreference to FIGS. 8A, 8B, and 8C.

The channel layer 128 may include a material of which an energy band gapis smaller than that of the second buffer layer 126. In some exemplaryembodiments, the channel layer 128 may include a material of which anenergy band gap is smaller than those of the first and second bufferlayers 122 and 126. The channel layer 128 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound.

The barrier layer 132 may include a material of which an energy band gapis greater than that of the channel layer 128. That is, in exemplaryembodiments, the channel layer 128 may include the material of which theenergy band gap is smaller than those of the barrier layer 132 and thesecond buffer layer 126, so the channel layer 128 may have a quantumwell structure. The barrier layer 132 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound. Inother exemplary embodiments, forming the barrier layer 132 may beomitted.

The channel layer 128 and the barrier layer 132 may be formed asdescribed with reference to FIG. 4.

Referring to FIGS. 20A, 20B, and 20C, the barrier layer 132, the channellayer 128, the second buffer layer 126, the graphene layer 124 includingthe first to third doped regions r1, r2 and r3, and the first bufferlayer 122 may be successively patterned to form active patterns AP1,AP2, and AP3 on the substrate 100. During the patterning process, anupper portion of the substrate 100 may be recessed. During thepatterning process, the graphene layer 124 may be patterned to form afirst doped pattern 104 a including the first doped region r1, a seconddoped pattern 104 b including the second doped region r2, and a thirddoped pattern 104 c including the third doped region r3. The activepatterns AP1, AP2, and AP3 may include a first active pattern AP1including the first doped pattern 104 a, a second active pattern AP2including the second doped pattern 104 b, and a third active pattern AP3including the third doped pattern 104 c.

Each of the active patterns AP1, AP2, and AP3 may include a first bufferpattern 102, a second buffer pattern 106, a channel pattern 108, and abarrier pattern 112 that are sequentially stacked on the substrate 100.According to the present exemplary embodiment, the first active patternAP1 may include the first doped pattern 104 a disposed between the firstand second buffer patterns 102 and 106 of the first active pattern AP1,and the second active pattern AP2 may include the second doped pattern104 b disposed between the first and second buffer patterns 102 and 106of the second active pattern AP2. The third active pattern AP3 mayinclude the third doped pattern 104 c disposed between the first andsecond buffer patterns 102 and 106 of the third active pattern AP3.

A device isolation layer ST covering sidewalls of the active patternsAP1, AP2, and AP3 may be formed on the substrate 100. According to anexemplary embodiment, the sidewalls of the active patterns AP1, AP2, andAP3 may not be exposed by the device isolation layer ST, as illustratedin FIG. 20C. According to another exemplary embodiment, each of theactive patterns AP1, AP2, and AP3 may include an upper portion (e.g., anactive fin AF) exposed by the device isolation layer ST, as illustratedin FIG. 21. In such exemplary embodiments, a height of a top surface STuof the device isolation layer ST may be lower than a height of a bottomsurface 104L of each of the first to third doped patterns 104 a, 104 b,and 104 c.

Referring again to FIGS. 15A to 15E, gate electrodes GE may be formed tointersect active patterns AP1, AP2, and AP3. The gate electrodes GE maybe provided on the active patterns AP1, AP2, and AP3 and may extend inthe second direction D2. In an exemplary embodiment, the gate electrodesGE may cover the top surfaces of the active patterns AP1, AP2, and AP3and the top surface of the device isolation layer ST, as illustrated inFIG. 15E. In another exemplary embodiment, each of the gate electrodesGE may cover the top surface and the exposed sidewalls of each of theactive patterns AP1, AP2, and AP3 and may extend onto the top surface ofthe device isolation layer ST, as illustrated in FIG. 15F. A gateinsulating pattern GI may be formed between each of the gate electrodesGE and each of the active patterns AP1, AP2, and AP3. A capping patternCAP may be formed on a top surface of each of the gate electrodes GE,and gate spacers GS may be formed on both sidewalls of each of the gateelectrodes GE. The gate insulating pattern GI, the gate electrodes GE,the capping patterns CAP, and the gate spacers GS may be formed by thesubstantially same method as described in the first embodiment withreference to FIGS. 1A to 1C. Thereafter, source/drain regions 110 may beformed in each of the active patterns AP1, AP2, and AP3 at both sides ofeach of the gate electrodes GE.

FIGS. 22A to 26A are plan views illustrating a method of forming asemiconductor device according to a fourth exemplary embodiment inaccordance with principles of inventive concepts. FIGS. 22B to 26B arecross-sectional views taken along lines I-I′ of FIGS. 22A to 26A,respectively. In the present exemplary embodiment, the same elements asdescribed in the formation method according to the first embodiment ofFIGS. 2 to 5 will be indicated by the same reference numerals or thesame reference designators. For the purpose of ease and convenience inexplanation, the descriptions to the same elements as in the formationmethod of the first embodiment will be omitted or only brieflydescribed.

As described with reference to FIG. 2, the first buffer layer 122 may befirst formed on the substrate 100. The first buffer layer 122 mayinclude silicon (Si), germanium (Ge), silicon-germanium (SiGe), or aIII-V group compound. A graphene layer 124 may be provided on the firstbuffer layer 122. As described with reference to FIGS. 7A, 7B, and 7C,the graphene layer 124 may be formed on the first support substrate 200and may be then provided onto the first buffer layer 122 by means of thetransfer process.

Referring to FIGS. 22A and 22B, the graphene layer 124 may be doped withan impurity IM to form a doped graphene layer 125. The doped graphenelayer 125 may include a plurality of doped regions r1, r2, and r3. Forexample, the doped regions r1, r2, and r3 may extend in a firstdirection D1 and may be arranged along a second direction D2intersecting the first direction D1. In some exemplary embodiments, aconductivity type of at least one of the doped regions r1, r2, and r3may be different from those of the others of the doped regions r1, r2,and r3. In other exemplary embodiments, the doped regions r1, r2, and r3may have the same conductivity type, but an impurity concentration of atleast one of the doped regions r1, r2, and r3 may be different fromthose of the others of the doped regions r1, r2, and r3. In still otherexemplary embodiments, the doped regions r1, r2, and r3 may have thesame conductivity type and the same impurity concentration.

Referring to FIGS. 23A and 23B, the doped graphene layer 125 may bepatterned to form a plurality of doped patterns 104. In an exemplaryembodiment, mask patterns (not shown) defining the doped patterns 104may be formed on the doped graphene layer 125, and an etching processmay be performed on the doped graphene layer 125 using the mask patternsas an etch mask to form the doped patterns 104. The first buffer layer122 between the doped patterns 104 may be exposed by the patterningprocess.

The doped patterns 104 may have bar shapes extending in the firstdirection D1 and may be arranged in the second direction D2 and may bespaced apart from each other. According to an exemplary embodiment, aconductivity type of at least one of the doped patterns 104 may bedifferent from those of the others of the doped patterns 104. Accordingto another exemplary embodiment, the doped patterns 104 may have thesame conductivity type, but the impurity concentration of at least oneof the doped patterns 104 may be different from those of the others ofthe doped patterns 104. According to still another exemplary embodiment,the doped patterns 104 may have the same conductivity type and the sameimpurity concentration.

Referring to FIGS. 24A and 24B, a second buffer layer 126 may be formedon the first buffer layer 122. The second buffer layer 126 may fillspaces between the doped patterns 104 and may extend onto top surfacesof the doped patterns 104. According to the present exemplaryembodiment, the second buffer layer 126 may be formed by performing aselective epitaxial growth (SEG) process using the first buffer layer122 exposed by the doped patterns 104 as a seed. The second buffer layer126 may be grown in a direction parallel to a top surface of thesubstrate 100 during the SEG process, so the second buffer layer 126 maycover the top surfaces of the doped patterns 104. The second bufferlayer 126 may include silicon (Si), germanium (Ge), silicon-germanium(SiGe), or a III-V group compound, for example.

Referring to FIGS. 25A and 25B, the SEG process may be performed untilthe second buffer layer 126 completely covers the top surfaces of thedoped patterns 104, so the doped patterns 104 may be buried under thesecond buffer layer 126. Thereafter, a channel layer 128 and a barrierlayer 132 may be sequentially formed on the second buffer layer 126.

The channel layer 128 may include a material of which an energy band gapis smaller than that of the second buffer layer 126. In someembodiments, the channel layer 128 may include a material of which anenergy band gap is smaller than those of the first and second bufferlayers 122 and 126. The channel layer 128 may include silicon (Si),germanium (Ge), silicon-germanium (SiGe), or a III-V group compound.

The barrier layer 132 may include a material of which an energy band gapis greater than that of the channel layer 128. That is, the channellayer 128 may include the material of which the energy band gap issmaller than those of the barrier layer 132 and the second buffer layer126. As a result, in accordance with principles of inventive concepts,the channel layer 128 may have a quantum well structure. The barrierlayer 132 may include silicon (Si), germanium (Ge), silicon-germanium(SiGe), or a III-V group compound. In other exemplary embodiments,forming the barrier layer 132 may be omitted.

Referring to FIGS. 26A and 26B, the barrier layer 132, the channel layer128, the second buffer layer 126, and the first buffer layer 122 may besuccessively patterned to form active patterns AP on the substrate 100.During the patterning process, the second buffer layer 126 disposedbetween the doped patterns 104 may be etched but the doped patterns 104may not be etched. As a result, each of the active patterns AP mayinclude each of the doped patterns 104. That is, in exemplaryembodiments in accordance with principles of inventive concepts, each ofthe active patterns AP may include a first buffer pattern 102, the dopedpattern 104, a second buffer pattern 106, a channel pattern 108, and abarrier pattern 112 which are sequentially stacked on the substrate 100.

A device isolation layer ST may be formed on the substrate 100 to coversidewalls of the active patterns AP. Next, subsequent processes may beperformed. The subsequent processes of the present embodiment may be thesubstantially same as the formation processes described with referenceto FIGS. 1A to 1C, 9A to 9D, and 15A to 15E.

According to exemplary embodiments of inventive concepts, extra carriersmay be provided to the channel pattern using the doped pattern that isformed of the graphene doped with the impurity, and, in accordance withprinciples of inventive concepts , the electrical conductivity of thechannel pattern may be increased to improve the operating characteristicof the transistor. In addition, the doped pattern may have the thicknessof one atomic layer by the two-dimensional crystal structure of thegraphene, so the characteristic dispersion of the transistor may beimproved. Furthermore, heat generated from the transistor including thedoped pattern may be easily dissipated by the high thermal conductivityof the graphene.

In addition, the graphene layer may be formed to include doped regionsthat are injected with impurities having different conductivity typesfrom each other, or which are injected with the impurities having thesame conductivity type but different impurity concentrations from eachother. Thereafter, the graphene layer may be patterned to form the dopedpatterns which have different conductivity types from each other, orwhich have the same conductivity type and different impurityconcentrations from each other. As a result, the semiconductorcomponents (e.g., the field effect transistors) including the samechannel material and having the different conductivity types from eachother may be easily realized using the doped patterns, or thesemiconductor components including the same channel material and havingthe different threshold voltages from each other may be easily realizedusing the doped patterns.

FIG. 27 is a schematic block diagram illustrating an electronic systemincluding a semiconductor device in accordance with principles ofinventive concepts.

Referring to FIG. 27, an electronic system 1100 according to anexemplary embodiment of inventive concepts may include a controller1110, an input/output (I/O) unit 1120, a memory device 1130, aninterface unit 1140, and a data bus 1150. At least two of the controller1110, the I/O unit 1120, the memory device 1130, and the interface unit1140 may communicate with each other through the data bus 1150. The databus 1150 may correspond to a path through which electrical data aretransmitted.

The controller 1110 may include at least one of a microprocessor, adigital signal processor, a microcontroller, or another logic devicehaving a similar function to any one thereof. The I/O unit 1120 mayinclude a keypad, a keyboard and/or a display device. The memory device1130 may store data and/or commands. The interface unit 1140 maytransmit electrical data to a communication network or may receiveelectrical data from a communication network. The interface unit 1140may operate with or without a wired connection. For example, theinterface unit 1140 may include an antenna for wireless communication ora transceiver for cable (or wired) communication. Although not shown inthe drawings, the electronic system 1100 may further include a fastdynamic random access memory (DRAM) device and/or a fast static randomaccess memory (SRAM) device which acts as a cache memory for improvingan operation of the controller 1110. At least one semiconductor devicein accordance with principles of inventive concepts may be provided inthe memory device 1130 or may be provided to the controller 1110 and/orthe I/O unit 1120.

The electronic system 1100 may be applied to a personal digitalassistant (PDA), a portable computer, a web tablet, a wireless phone, amobile phone, a digital music player, a memory card, or other electronicproducts receiving and/or transmitting information data by wireless.

According to exemplary embodiments in accordance with principles ofinventive concepts, extra carriers may be provided to a channel patternusing a doped pattern formed of graphene injected or implanted with animpurity. In this manner, in accordance with principles of inventiveconcepts, the electrical conductivity of the channel pattern may beincreased to improve the operating characteristic of a field effecttransistor. In addition, the doped pattern may have the thickness of oneatomic layer by the two-dimensional crystal structure of the graphene,so the characteristic dispersion of the field effect transistor may beimproved. Furthermore, heat generated from the transistor including thedoped pattern may be easily dissipated by the high thermal conductivityproperty of the graphene.

In addition, in accordance with principles of inventive concepts, thegraphene layer may be formed to include doped regions that are injectedwith impurities having different conductivity types from each other, orwhich are injected with impurities having the same conductivity type butdifferent impurity concentrations from each other. Thereafter, thegraphene layer may be patterned to form the doped patterns which havedifferent conductivity types from each other, or which have the sameconductivity type and different impurity concentrations from each other.As a result, the semiconductor components (e.g., the field effecttransistors) including the same channel material and having thedifferent conductivity types from each other may be easily realizedusing the doped patterns, or the semiconductor components including thesame channel material and having different threshold voltages from eachother may be easily realized using the doped patterns.

While inventive concepts have been described with reference to exemplaryembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of inventive concepts. Therefore, it should beunderstood that the above embodiments are not limiting, but illustrativeand the scope of inventive concepts are to be determined by the broadestpermissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdescription.

What is claimed is:
 1. A semiconductor device comprising: a deviceisolation layer provided on a substrate to define an active pattern; anda gate electrode provided on the active pattern and intersecting theactive pattern, wherein the active pattern comprises: a first bufferpattern on the substrate; a channel pattern on the first buffer pattern;a doped pattern between the first buffer pattern and the channelpattern; and a second buffer pattern between the doped pattern and thechannel pattern, wherein the doped pattern is configured to provideextra carriers to the channel pattern, and wherein a height of a bottomsurface of the device isolation layer is lower than a height of a bottomsurface of the first buffer pattern.
 2. The semiconductor device ofclaim 1, wherein the doped pattern has a conductivity type of a P-typeor an N-type.
 3. The semiconductor device of claim 1, wherein the dopedpattern has a crystal structure formed by substituting the impurity forsome of carbon atoms of the graphene.